Method of casting iron pigs



NITED STATES PATENT OEEICE.

METHOD OF CASTING IRO DIRECT AND MESNE OF ILLINOIS.

N PIGS, moors, 80C.

SPECIFICATION forming part of Letters P Application filed November 28, 1888.

To all whom it may concern:

Be it known that I, .TAMEs W. COLE, a citizen of the United States, and a resident of the city of St. Louis, in the State of Missouri, have invented a certain new and useful Improvement in Methods of Casting Iron Pigs, Ingots, &c., of which the following is a full, clear, and exact description. My invention relates to a process of treating iron, and more particularly to a process by which iron which has been decarburized or which is not thoroughly saturated with carbon maybe supplied with the desired proportion of carbon and otherwise improved without the introduction of foreign impurities or other agents, such as manganese or silicon.

In the production of cast-iron for foundry use it is usually desirable to provide a pigiron as thoroughly saturated with graphitic carbon as it is possible to secure under the conditions of smelting in a blast-furnace; but on remelting in a cupola for the purpose of casting it is found that there is a decrease in the amount of carbon, silicon, and manganese and an increase in the amount of sulphurcontainedin the metal. Of these changes the decrease in the amountof manganese tends to the formation of gray iron; but its action is quite feeble, and is much more than overpowered by the other changes, all of which favor the formation of white iron, so that as a linal result there is a strong tendency toward the formation of white iron and the production of castings hard and brittle and of a tensile strength approximately less than the original character of the pig-iron would justify. A second and third remelt of such a casting increases its brittle character, so that iron thus subjected to the remelt is classed as scrap-iron, and is of slight value, except for the commoner kind of casting.

My invention has for its object, therefore, to increase the percentage of carbon and even saturate iron when in an incompletely-saturated condition or when decarburized with carbon in such a manner as to increase the tensile strength and density of the iron, and at the same time to counteract the tendency to hardening which usually goes with an inatent No. 468,292, dated February 2, 1892.

Serial No, 292,125. (Specimens) creased tensile strength, and even to reduce its normal hardness.

Incidentally I seek by my process to provide a mode of casting iron in metallic molds without chilling. I have ascertained that iron when in a molten condition and at a temperature at which it runs freely viz., a temperature of about 3,000 Fahrenheit or upward-when brought into contact with carbonaceous material in a pulverulent condition acts to dissolve the carbon, which becomes incorporated into the iron, and that if a sufficient quantity of pulverized carbon is acted upon a distinct and material change in the character of the iron takes place throughout, contributing a material increase in its tensile strength, causing a material increase in the softness of the iron and a density or fineness of grain of the product very noticeable on mere inspection. Other changes also take place in the metal the exact nature of which I have not yetbeen able to ascertain; but I believe that the finely-divided carbon exerts a reducing action upon the slag and oxides entangled in the iron and causes their re moval.

In carrying out my process I find it best to introduce the pulverized carbon in the form of graphite, plumbago, or the like, and in as fine a state of division as can practically.be obtained into metallic molds, by coating the interior of the mold with a paste composed of pulverized carbon and water, with or without gum-arabic or an analogous substance, to insure its adhering, to the wall of the mold, thereupon to subject the mold to heat for the purpose of evaporating the water, and finally, while the mold is still hotsay atatemperature of 200 Fahrenheit, or thereabont-to introduce molten iron having a temperature of not less than about 3,000 Fahrenheit, and preferably approaching the highest temperature obtainable in the cupola-to wit, 4,000" or upward. The iron is then allowed to cool in the ordinary manner, and the casting is found to present the characteristics of increased tensile strength, softness, and density before mentioned.

Another mode under whichI have successfully efiected the operation on iron remelted zoo in a cupola has been to prepare ingot-pans, each capable of holding an ingot of, say, one hundred pounds, by coating such pans with pulverized carbonaceous material, (graphite or plumbago,) combined into a paste with water and sometimes with and sometimes without a small amount of gum-arabic or other analogous substance, heating the pans, and thereupon introducing the iron in a molten condition and at a high temperature. The ingot thus produced is thoroughly saturated with carbon and may be remelted in the cupola for recasting.

Different irons require, for the best results from the treatment, the employment of different proportions of pulverized carbon; but it may be stated, as a general rule, that the treatment with graphite in a proportion of upward of one thirty-second of one per cent, but ordinarily not exceeding two or two and onehalf per cent, may be used with full benefit. In the treatment of scrap-iron, usually bought its character, the process has been very successfully carried on with about one-tenth of one per cent. of pulverized carbon, by weight. In the treatmentof certain pigssuoh as Bay View pigwi1en one-fourth of one per cent. of pulverized graphite was introduced in the mold it was found that the entire quantity the iron, the calcula tion, made under difficulties, indicating that perhaps onetwelfth of one per cent. had been taken up, leaving the rest in the form of a deposit on the sides of the mold. It is apparent, therefore, that by increasing the thickness of the pulverulent liningto provide a quantity of carbon in excess of the amount which the ironwill take successive castings under the process may be made in the same mold after one application of carbon thereto. The peculiar action which takes place in the iron while undergoing the changes due to the operation of this process is readily observable if, instead of running the iron into the ingotpan, where it is to solidify, or into the casting-mold, it shall be run into the ladle, which has previously been supplied with a coating of carbonaceous material in a pulverulent condition and practicallya' free state. From the ladle it will be quite apparent that the iron may be run into molds or into an ingotpan, also treated or not. This operation of treating in the ladle is not claimed herein, as it forms the subject-matter of-a concurrent application for Letters Patent filed December 5, 1891, Serial No. 414,161. If the temperature of the metallic mold is slightly raised, no chilling results. In practicing the process in this mannerit is observed that the iron thus introduced into the ladle undergoes a peculiar agitation or ebullition not observable when the same iron is introduced at the same temperature into a ladle not so prepared, and that the molten iron retains its fluidity for a much longer time than the iron in the untreated ladle. As a result the metal may be softness, and density,

. than a high poured into light and intricate castings with a facility equal to that obtained with an iron high in phosphorus, and the castings thus produced possess relatively thesame increased tensile strength, softness, and density observable with the castings made in the prepared mold direct without previous treatment in the ladle. A great practical advantage results from this prolonged fluidity, as it permits the ladle to be carried agreater distance than is possible under the common practice without such congelation of the metal as will interfere with the production of a good casting.

As before stated, any kind of pig or scrap iron can be eifectively treated and improved so as to have an increased tensile strength, but the proportion of improvement varies in inverse ratio to the quality of the original metal. A low grade of pig is improved to a much greater degree grade of pig. Underall circumstances I find it necessary that the carbon shall be finely divided, not exceeding in granular dimension fairly-fine sand, and under the conditions of heat possible in carrying on the process at the cupola it is desirable that the carbon shall be reduced to the finest practicable state of division, as before mentioned.

The samples which are filed with themesent application are made from No.3 Bay View pig, remelted, and at a temperature of about 3,500 Fahrenheit introduced into a metal (cast-iron) mold holding about six pounds, into which had been previously introduced about one-fifth of one per cent, by weightsay ninety-six grains-of carbon (pluinbago) in a finely-pulverized condition. The carbon was mixed with water into a paste,to which was added a very small proportion of gumarabic, and while in this condition was applied to the mold with a brush, thus being spread uniformly throughout the mold. The latter was thereupon heated to about 150 Fahrenheit, and the Bay View iron, at the temperature named, was introduced into the mold. The samples on file represent a piece of the original pig, a piece of the iron run into a sand mold without treatment, and a previously coated, as stated. The two samples of castings were taken from the same ladle and the conditions of pouring were identical to both.

The untreated casting shows, on analysis, the following composition: total carbon, 3.351; graphite, 3.063; silicon, 2.137; phosphorus, 0.750; tensile strength, (average two samples,) 18,5245 pounds per square inch. One sample showed a tensile strength of 18,449 and the other 18,600.

The treated sample, which can be readily distinguished from the other by the very noticeable increase in density and softness, shows, on analysis, the following composition: total carbon, 3.392; graphite, 2.853; silicon, 2.021; phosphorus, 0.689; tensile strength, (average two samples,) 28,622 pounds per iIo square inch. One sample showed a tensile strength of 28,722 and the other 28,522. The analysis shows a material increase in combined carbon. There is an increasein tensile strength of the iron of 10,0975 pounds, or about fifty-five per cent, while the treated iron is softer than the untreated as the results of this process. It may be stated that a mixture of scrap and pig iron subjected to this treatment showed an increase of about fifty per cent. in tensile strength, accompanied by an increase in softness and density.

The process herein described is to be carefully distinguished from the process in common use, by which the exterior of acasting has been given a smoother surface by dusting a small portion of powdered graphite on the interior of the mold. Under this process no change in the constitution of the iron was sought or effected, neither of the essential conditions of heat nor quantity apparently being present. The purpose was different and the quantity of graphite was too slight to exert any noticeable effect in the line of improvement which forms the subject of this invention. My invention is also to be carefully distinguished from any process in which the carbon is rendered hard and slaty by the association with it of oil, clay, or other substance, since it is essential for success with my process that the carbon be in a finely-divided stateand the particles easily surrounded and absorbed by the metal.

I am aware of aprocess by which a coating essentiallysolid in its character and ofa thickness of a half-inch, or thereabout, has been provided on the interior of molds to serve for heat non-conducting purposes in the process of casting; but, as will be apparent, such a procedure is foreign to my invention and is not to be included therein. It is probable that the non-conductive character of plumbago contributes an advantage in the practice of my process to the extent that it assists in preventing the chill of the iron at the surface adjacent to the mold; but this effect, if obtained, is a minor feature of my invention. By none of the processes above named, as existing before my invention, or any other process heretofore practiced with which I am familiar has the very marked improvement above mentioned been obtained, and the importance of the invention arises, not only from the remarkable character of the product, but from the fact that the practicing of the process under ordinary circumstances involves an insignificant additional expense to the ordinary cost of treatment. It will be re membered that the commercial value of iron is largely governed byits tensile strength and the ease with which it may be manipulated in the foundry and machine-shop. The loss due to the treatment by myprocess is so slight that it may be disregarded.

\Vhat I claim as new, and desire to secure by Letters Patent, is

l. The process of treating iron, which consists in introducing pulverulent carbonaceous material into a vessel, raising the temperature of the iron to a point at which it will flow freely, and while in this condition bringing the same in contact with the carbonaceous material andthereupon permitting the carbonaceous material to act upon the iron, substantially as described.

2. The process of treating iron which has been cast and permitted to solidify, which consists in remelting the iron and raising its temperature to a point at which it will flow freely, introducing pulverulent carbonaceous material into a vessel, bringing the iron while in the condition named into contact with the carbonaceous material, and thereupon permitting the carbonaceous material to act upon the iron, substantially as described.

3. The process of treating iron, which consists in introducing pulverulent carbonaceous material into a receptacle, raising the temperature of iron to a point at which itwill flow freely and while in this condition conveying it to the receptacle containing carbonaceous material, permitting the carbon to act upon the iron and allowing the iron to solidify, and thereupon removing and remelting the iron, substantially as described.

4. The process of treating iron, which consists in coating a metallic receptacle with pul verized carbonaceous material in substantially the proportion named, thereupon introducing into said receptacle molten iron at a temperature at which it will flow freely, and allowing the same to solidify without removal, substantially as described.

5. The process of producing castings, which consists in introducing pulverulent carbonaceous material into a vessel and introducing molten iron into said vessel at a temperature at which it will flow freely, permitting the carbonaceous material to act upon the iron, and permitting the iron to solidify, thereupon remelting the iron and introducing the same into a metallic mold having an interior coating of pulverulent carbonaceous material, substantially as described.

JAMES COLE. Witnesses:

SAML. KNIGHT, Enw. S. KNIGHT.

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